Crushers are used to crush waste materials (to-be-crushed objects) such as waste wood, etc. for the main purpose of recycling of the waste materials and of reducing the volume thereof. One example of such crushers is known that is provided with a crushing apparatus including a crushing rotor arranged with crushing bits (rotating blades) on the outer circumferential portion thereof and an anvil (fixed blade) provided on the outer circumferential side of the crushing rotor.
A crusher of this type is as below for example. A housing provided with an anvil is held by a shear pin, and during the crushing work, when an excessive impactive force is applied to the fixed blade in such a case where foreign object (a metal block, etc.) may mix in to-be-crushed object and may be held between the bit of the crushing rotor and the fixed blade of the housing, the shear pin is broken to retreat the housing. Thus, the crusher (the fixed blade, etc.) is prevented from being damaged. (See patent document 1.)    JP, A 2005-319349